Multi-membered reduction sheet metal ducts for transport of gaseous materials are known; however such ducts are relatively expensive to manufacture due to waste resulting from the cutting of separate pieces of sheet metal as well as the time and technique required to assemble the individual pieces. Further, these multiple piece units are subject to excessive gas leakage through the assembled joints unless further expense is incurred by welding or otherwise sealing the end margins of the joined members. Additionally, the lack of rigidity and strength associated with these multiple piece reduction devices makes them subject to rupture during intermittent surges in gas flow velocity.
Accordingly it is an object of this invention to overcome the above disadvantages by providing a stronger reduction device while eliminating the expense of cutting, assembling and welding separate pieces.
These and other advantages will become apparent from the following description and disclosure.
The invention relates to an improved reducing duct composed of sheet metal for the transfer of gaseous material between pipes of different internal diameter and/or shape. Accordingly the present invention is a unitary joint adapted for union between piping of ovate and annular contour as well as between pipes of the same shape but of different diameters. The present duct comprises an end portion representing substantially at least xe2x85x9c the length of the duct and defined as an annular, inwardly tapered and fluted or corrugated section and an opposite end portion of an annular non-corrugated vertical section, said sections integrally united in a continuous manner through an intermediate annular reinforcement ring. Substantially xe2x85x9 to about xc2xc of the corrugated section at its free end is preferably non-tapered to simplify subsequent alignment and mounting of a pipe having a smaller diameter than a pipe ostensibly mounted at the opposite end of the duct.